1. Field of the Invention
The invention relates to a light emitting diode device and a manufacturing method thereof.
2. Description of the Related Art
A light emitting diode (LED) device is a semiconductor luminescent device, providing many advantageous features such as low power consumption, long lifetime, short response time, and so on. The sizes of LED devices are so small that they are easily manufactured to very small devices. Thus, with the continuous improvement of the technology recently, applications of LED devices have been applied in indicator lights of computers or home appliances, back light units of liquid crystal display device, traffic signals, or indicator lights of cars.
According to the prior art, in order to improve luminescence efficiency of LED devices, metal reflective substrates are disposed on LED devices reflecting light to improve luminescence efficiency. However, there are some problems with such LED devices which need to be solved.
FIG. 1 shows the LED device disclosed in Taiwan Patent No. 0544958. The LED device includes a metal reflective substrate 801 and a stacked structure on the metal reflective substrate 801. The stacked structure sequentially includes a first reaction layer 802, a transparent bonding layer 803, a second reaction layer 804, a transparent conductive layer 805, a first contact layer 806, a p-type epitaxial layer 807, a light emitting layer 808, an n-type epitaxial layer 809, and a second contact layer 810. In addition, an electrode 811 and an electrode 812 are disposed on the second contact layer 810 and the transparent conductive layer 805, respectively.
The LED device is formed by bonding the first reaction layer 802 with the second reaction layer 804 through the transparent bonding layer 803 and bonding the metal reflective substrate 801 with the first reaction layer 802. However, since the transparent bonding layer 803 is made of plastic materials, the heat generated from the LED device can not transfer to the metal reflective substrate 801 and dissipate effectively. As a result, the efficiency of the LED device dramatically decreases when the heat inside the LED device continuously accumulates.
Additionally, in the dicing process, a plurality of LED devices are obtained by dicing the metal reflective substrate 801 and the stacked structure. However, the metal particle produced in the dicing process can adhere to the sidewalls of the stacked structure and thus increase the leakage current of the stacked structure.
FIG. 2 shows the LED device disclosed in Taiwan Patent No. 0543210. The LED device is formed by bonding a light emitting diode stacked structure 902 with a metal reflective substrate 903 through a metal bonding layer 901. The bonding of the metal bonding layer 901 with the metal reflective substrate 903 requires a high temperature and high pressure, which, however causes inter-diffusion between the light emitting diode stacked structure 902 and the metal reflective substrate 903. In addition, the leakage current of the light emitting diode stacked structure 902 can increase due to the dicing process.
The two conventional LED devices above are both fabricated by forming the stacked epitaxial structure on an epitaxial substrate, then disposing the stacked epitaxial structure on a glass substrate or an electroplating substrate through a replacement process, and then dicing into individual LED devices. Thus, while an additional dicing process is needed for the method described, the probability of metal particles adhering to the sidewalls of the stacked structure is high.